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- GALAXIES: QUASARS: EMISSION LINES (2)
- Galaxies: Quasars: Emission Lines (2)
- ISM: ABUNDANCES (2)
- ISM: Abundances (2)
- Stars (2)
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- Algorithms (1)
- Atomic data (1)
- Axial density profile (1)
- Band-gap (1)
- CERN (1)
- CERN neutrino beam (1)
- COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE (1)
- Catalogs (1)
- Cell (1)
- Cool giants (1)
- Cosmology (1)
- Cosmology: Large-Scale Structure of Universe (1)
- Damping (1)
- Energy (1)
- Enhancement effects (1)
- Fe/H (1)
- GALAXIES: QUASARS: GENERAL (1)
- GALAXIES: SEYFERT (1)
- Galaxies: Quasars: General (1)
- Galaxies: Seyfert (1)
- GeV protons (1)
- Ginzburg-landau theory (1)
- Gravitation – methods: data analysis – pulsars: general – pulsars: individual: PSR 0437-4715 (1)
- ISM: ATOMS (1)
- ISM: Atoms (1)
Articles 1 - 25 of 25
Full-Text Articles in Physics
Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos
Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos
Dartmouth Scholarship
We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective evolution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdamped regime, the dissipative kernel in the field equation of motion is closely related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a time-dependent Ginzburg-Landau description of the approach to equilibrium …
Quasars As Cosmological Probes: The Ionizing Continuum, Gas Metallicity, And The WΛ-L Relation, Kirk Korista, Jack Baldwin, Gary J. Ferland
Quasars As Cosmological Probes: The Ionizing Continuum, Gas Metallicity, And The WΛ-L Relation, Kirk Korista, Jack Baldwin, Gary J. Ferland
Physics and Astronomy Faculty Publications
Using a realistic model for line emission from the broad emission line regions of quasars, we are able to reproduce the previously observed correlations of emission-line ratios with the shape of the spectral energy distribution (SED). In agreement with previous studies, we find that the primary driving force behind the Baldwin effect (Wλ ~ Lβ, β < 0) is a global change in the SED with quasar luminosity, in that more luminous quasars must have characteristically softer ionizing continua. This is completely consistent with observations that show (1) a correlation between Luv, αox, and αuvx (2) correlations of SED shape-sensitive line ratios with αox, αuvx, and Luv; and (3) correlations between line equivalent widths and αox, αuvx …
Temperature Fluctuations In Photoionized Nebulae. Ii. The Effect Of Inhomogeneous Abundances, J. B. Kingdon, Gary J. Ferland
Temperature Fluctuations In Photoionized Nebulae. Ii. The Effect Of Inhomogeneous Abundances, J. B. Kingdon, Gary J. Ferland
Physics and Astronomy Faculty Publications
Recent abundance determinations based on recombination lines in several emission-line nebulae yield ionic abundances several times larger than those derived from forbidden lines. These results cast uncertainty over all abundance determinations in such objects. One possible explanation for these discrepancies frequently cited in the literature is the presence of chemical inhomogeneities. We have run a series of photoionization models to examine what effect such inhomogeneities will have on the resulting temperature structure of nebulae. We then derive abundances from these models, utilizing Peimbert's t2 formalism. Our results suggest that, although chemical inhomogeneities may produce nonnegligible biases in abundance determinations …
Cross Sections Fall 1998, Department Of Physics And Astronomy
Cross Sections Fall 1998, Department Of Physics And Astronomy
Cross Sections
No abstract provided.
A Zero Point And Accidental Errors For Published Values Of [Fe/H] For Cool Giants, B. J. Taylor
A Zero Point And Accidental Errors For Published Values Of [Fe/H] For Cool Giants, B. J. Taylor
Faculty Publications
This paper is one of a series based on published values of [Fe/H] for late-type evolved stars. Only values of [Fe/H] from high-dispersion spectroscopy or related techniques are used. The narrative in this paper begins at a point where mean values of [Fe/H] have been derived for xiVir, alphaBoo, betaGem, and the Hyades giants. By using these stars as standard stars when necessary, a zero-point data base is assembled. This data base is then expanded into its final version by correcting and adding additional data in a step-by-step process. As that process proceeds, data comparisons are used to establish rms …
An Analysis Of Temperature Dependent Photoluminescence Line Shapes In Ingan, John S. Colton, K. L. Teo, P. Y. Yu, E. R. Weber, M. F. Li, W. Lui, K. Uchida, H. Tokunaga, N. Akutsu, K. Matsumoto
An Analysis Of Temperature Dependent Photoluminescence Line Shapes In Ingan, John S. Colton, K. L. Teo, P. Y. Yu, E. R. Weber, M. F. Li, W. Lui, K. Uchida, H. Tokunaga, N. Akutsu, K. Matsumoto
Faculty Publications
Photoluminescence (PL) line shapes in InGaN multiple quantum well structures have been studied experimentally and theoretically between 10 and 300 K. The higher temperature PL spectra can be fitted qualitatively with a thermalized carrier distribution and a broadened joint-density-of-states. The low temperature PL line shapes suggest that carriers are not thermalized, as a result of localization by band-gap fluctuations. We deduce a localization energy of ~7 meV as compared with an activation energy of ~63 meV from thermal quenching of the PL intensity. We thus conclude that this activation energy and the band-gap fluctuation most likely have different origins.
Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor
Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor
Faculty Publications
A catalog of mean values of [Fe/H] for evolved G and K stars is described. The zero point for the catalog entries has been established by using differential analyses. Literature sources for those entries are included in the catalog. The mean values are given with rms errors and numbers of degrees of freedom, and a simple example of the use of these statistical data is given. For a number of the stars with entries in the catalog, temperatures have been determined. A separate catalog containing those data is briefly described.
Polarization Of Astronomical Maser Radiation. Iv. Circular Polarization Profiles, Moshe Elitzur
Polarization Of Astronomical Maser Radiation. Iv. Circular Polarization Profiles, Moshe Elitzur
Physics and Astronomy Faculty Publications
Profile comparison of the Stokes parameters V and I is a powerful tool for maser data analysis, which provides the first direct methods for unambiguous determination of (1) the maser saturation stage, (2) the amplification optical depth and intrinsic Doppler width of unsaturated masers, and (3) the comparative magnitudes of Zeeman splitting and Doppler line width. Circular polarization recently detected in OH 1720 MHz emission from the Galactic center appears to provide the first direct evidence for maser saturation.
Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic
Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic
Articles
Stark parameters (width and shift) of four doubly ionized nitrogen spectral lines, that belong to 3s-3p and 3p-3d transitions (lower multiplets), have been measured in a linear pulsed, low pressure, arc discharge in the nitrogen-oxygen and helium-nitrogen-oxygen plasmas in a (30 000 - 54 000) K electron temperature and a (0.75 1023 - 2.8 1023) electron density ranges. The measured values have been compared to the existing experimental and calculated data.
Statistics Of Active Galactic Nuclei In Rich Clusters Revisited, M. Way, R. Flores, H. Quintana
Statistics Of Active Galactic Nuclei In Rich Clusters Revisited, M. Way, R. Flores, H. Quintana
Physics Faculty Works
Using the spectrophotometry of a large sample of galaxies in 19 Abell clusters, we have selected 42 candidate active galactic nuclei (AGNs) using the criteria used by Dressler and coworkers in their analysis of the statistics of 22 AGNs in 14 rich cluster fields, which are based on the equivalent width of [O II] 3727 Å, Hβ, and [O III] 5007 Å emission. We have then discriminated AGNs from H II region-like galaxies (hereafter H II galaxies) in the manner developed by Veilleux & Osterbrock using the additional information provided by Hα and [N II] 6583 Å or Hα and …
Search For A New Gauge Boson In Π0 Decays, Nomad Collaboration, J. Altegoer, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Boyd, A. Bueno, S. Bunyatov, L. Camilleri, K. Zuber, Roberto Petti, Et. Al.
Search For A New Gauge Boson In Π0 Decays, Nomad Collaboration, J. Altegoer, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Boyd, A. Bueno, S. Bunyatov, L. Camilleri, K. Zuber, Roberto Petti, Et. Al.
Faculty Publications
A search was made for a new light gauge boson X which might be produced in π0→γ+X decay from neutral pions generated by 450 GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of X→π0 conversion in the external Coulomb field of a nucleus. With 1.45×1018 protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in …
Cross Sections Spring 1998, Department Of Physics And Astronomy
Cross Sections Spring 1998, Department Of Physics And Astronomy
Cross Sections
No abstract provided.
Temperature Variations And N/O In The Orion Nebula From Hst Observations, R. H. Rubin, P. G. Martin, R. J. Dufour, Gary J. Ferland, J. A. Baldwin, J. J. Hester, D. K. Walter
Temperature Variations And N/O In The Orion Nebula From Hst Observations, R. H. Rubin, P. G. Martin, R. J. Dufour, Gary J. Ferland, J. A. Baldwin, J. J. Hester, D. K. Walter
Physics and Astronomy Faculty Publications
Using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS) on the Hubble Space Telescope, we measured the flux of the N II] (2s2p3 5S2 --> 2s22p2 3P2,1) lines at λvac = 2143.45, 2139.68 Å in the Orion Nebula--the first detection of these lines in an H II region. In order to assess the N+/O+ ratio, we also measured the flux of the [O II] (2p32Po1/2,3/2-->2p34So3/2) lines at λvac …
The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland
The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland
Physics and Astronomy Faculty Publications
We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of active galactic nuclei (AGNs). An important albedo source in moderately ionized ionization-bounded clouds is that which is due to neutral hydrogen: Rayleigh scattering of continuum photons off the extreme damping wings of Lyα. The photons resulting from this scattering mechanism may contribute significantly to the Lyα emission line, especially in the very broad wings. In addition, line photons emitted near 1200 Å (e.g., N V λ1240) that stream toward the neutral portion of …
The Nomad Experiment At The Cern Sps, Nomad Collaboration, J. Altegoer, M. Anfreville, C. Angelini, P. Astier, M. Authier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Bunyatov, S. Boyd, Roberto Petti, Et. Al.
The Nomad Experiment At The Cern Sps, Nomad Collaboration, J. Altegoer, M. Anfreville, C. Angelini, P. Astier, M. Authier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, G. Ballocchi, M. Banner, S. Basa, G. Bassompierre, K. Benslama, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Bunyatov, S. Boyd, Roberto Petti, Et. Al.
Faculty Publications
The NOMAD experiment is a short base-line search for νμ − ντ oscillations in the CERN neutrino beam. The ντ's are searched for through their charged current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation …
Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer
Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer
Faculty Publications
Global thermal equilibrium computations are presented for non-neutral plasmas whose radial size is much larger than their axial thickness. Axial and radial density profiles are computed for both ideal and nonideal Penning trap fields. Simple results are obtained in the limits of both low and high central density. Comparison is made to the grid calculations of Mason et al. [Phys. Plasmas 3 (5), 1502 (1996)].
Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms, Alejandro Garcia, F. Alexander, B. Alder
Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms, Alejandro Garcia, F. Alexander, B. Alder
Faculty Publications
Using the Green–Kubo theory, the dependence of the viscosity and thermal conductivity on cell size is obtained explicitly for stochastic particle methods such as direct simulation Monte Carlo (DSMC) and its generalization, the consistent Boltzmann algorithm (CBA). These analytical results confirm empirical observations that significant errors occur when the cell dimensions are larger than a mean free path.
Solar Cycle Variability Of Hot Oxygen Atoms At Mars, Jhoon Kim, Andrew F. Nagy, Jane L. Fox, Thomas E. Cravens
Solar Cycle Variability Of Hot Oxygen Atoms At Mars, Jhoon Kim, Andrew F. Nagy, Jane L. Fox, Thomas E. Cravens
Physics Faculty Publications
The population of hot oxygen atoms in the Martian exosphere is reexamined using newly calculated hot O production rates for both low and high solar cycle conditions. The hot oxygen production rates are assumed to result from the dissociative recombination of O2+ ions. These calculations take into account the calculated vibrational distribution of O2+ and the new measured branching ratios. Furthermore, these calculations also consider the variation of the dissociative recombination cross section with the relative speed of the participating ions and electrons, the rotational energy of the O2+ ions, and the spread of …
Inversion Of Plasmaspheric Euv Remote Sensing Data From The Stp 72-1 Satellite, R.R. Meier, A.C. Nicholas, J.M. Picone, D.J. Melendez-Alvira, G. Ganguli, Mark Anthony Reynolds, E.C. Roelof
Inversion Of Plasmaspheric Euv Remote Sensing Data From The Stp 72-1 Satellite, R.R. Meier, A.C. Nicholas, J.M. Picone, D.J. Melendez-Alvira, G. Ganguli, Mark Anthony Reynolds, E.C. Roelof
Publications
Observations of the extreme ultraviolet emission of helium ions at 30.4 nm can be used to study the global shape of the plasmasphere and its dynamical response to geomagnetic forcing. In order to retrieve number densities of plasmaspheric He+ from such observations, we have developed a new inversion technique based on discrete inverse theory, which uses the optical data to optimize a parameterized model of the He+ distribution. We apply this inversion technique to several orbits of data obtained from the Naval Research Laboratory extreme ultraviolet photometric experiment launched on the STP 72-1 satellite in October 1972. The inversion is …
Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries: Extension To Post-Newtonian Waveforms, Soumya Mohanty
Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries: Extension To Post-Newtonian Waveforms, Soumya Mohanty
Physics and Astronomy Faculty Publications and Presentations
The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (one step search) is used. In an earlier paper we presented a detection strategy, called a two step search, that utilizes a hierarchy of template banks. It was shown that in the simple case of a family of Newtonian signals, an on-line two step search was ≃8 times faster than an on-line one step search (for the initial LIGO). In this paper we extend the two step search to the more realistic case of …
A Data Analysis Approach For Detecting Gravitational Waves From Psr 0437-4715, Soumya Mohanty, I. S. Heng, David Blair, S. Dhurandhar, M. Tovar, E. Ivanov
A Data Analysis Approach For Detecting Gravitational Waves From Psr 0437-4715, Soumya Mohanty, I. S. Heng, David Blair, S. Dhurandhar, M. Tovar, E. Ivanov
Physics and Astronomy Faculty Publications and Presentations
A search for gravitational waves from the millisecond pulsar PSR 0437-4715 has been initiated using the bar detector NIOBE which is located at the University of Western Australia. We present a detailed report on the data analysis algorithm, called phase plane rotation, which will be used in this search. A discussion of the actual implementation of the algorithm is presented. The data analysis algorithm mentioned above has the advantage that it requires minimal changes to the already-existing data acquisition facility of NIOBE but, at the same time, it is as efficient as optimal filtering in detecting a signal. This …
Searching For Periodic Sources With Ligo, Patrick R. Brady, Teviet Creighton, Curt Cutler, Bernard F. Schutz
Searching For Periodic Sources With Ligo, Patrick R. Brady, Teviet Creighton, Curt Cutler, Bernard F. Schutz
Physics and Astronomy Faculty Publications and Presentations
We investigate the computational requirements for all-sky, all-frequency searches for gravitational waves from spinning neutron stars, using archived data from interferometric gravitational wave detectors such as LIGO. These sources are expected to be weak, so the optimal strategy involves coherent accumulaton of signal-to-noise using Fourier transforms of long stretches of data (months to years). Earth-motion-induced Doppler shifts, and intrinsic pulsar spindown, will reduce the narrow-band signal-to-noise by spreading power across many frequency bins; therefore, it is necessary to correct for these effects before performing the Fourier transform. The corrections can be implemented by a parametrized model, in which one does …
Ab Initio Single- And Multiple-Scattering Exafs Debye-Waller Factors: Raman And Infrared Data, N. Dimakis, Grant Bunker
Ab Initio Single- And Multiple-Scattering Exafs Debye-Waller Factors: Raman And Infrared Data, N. Dimakis, Grant Bunker
Physics and Astronomy Faculty Publications and Presentations
The extended x-ray-absorption fine structure (EXAFS) Debye-Waller factor is an essential term appearing in the EXAFS equation that accounts for the molecular structural and thermal disorder of a sample. Single- and multiple-scattering Debye-Waller factors must be known accurately to obtain quantitative agreement between theory and experiment. Since the total number of fitting parameters that can be varied is limited in general, data cannot support fitting of all relevant multiple-scattering Debye-Waller factors. Calculation of the Debye-Waller factors is typically done using the correlated Debye approximation, where a single parameter (Debye temperature) is varied. However, this procedure cannot account in general for …
Critical Casimir Forces Between Spherical Particles In Fluids, Andreas Hanke, F. Schlesener, E. Eisenriegler, S. Dietrich
Critical Casimir Forces Between Spherical Particles In Fluids, Andreas Hanke, F. Schlesener, E. Eisenriegler, S. Dietrich
Physics and Astronomy Faculty Publications and Presentations
Long-ranged correlations in a fluid close to its critical point Tc cause distinct forces between immersed colloidal particles and the container walls. We calculate such a force and its temperature dependence for the generic case of a spherical particle located at a distance D from a planar wall and find that the force attains a maximum at a temperature Tmax(D) above Tc, which facilitates quantitative experimental tests. The corresponding effective pair interaction between the colloidal particles themselves, potentially leading to aggregation, is also discussed.
Time-Resolved Studies Of Ultracold Ionizing Collisions, Scott D. Bergeson, C. Orzel, S. Kulin, S. L. Rolston
Time-Resolved Studies Of Ultracold Ionizing Collisions, Scott D. Bergeson, C. Orzel, S. Kulin, S. L. Rolston
Faculty Publications
Using 40 ns laser pulses, we probe the real-time dynamics of ultracold ionizing collisions in metastable xenon. We time resolve both shielding and enhancement effects, and observe the production of Xe2^+ molecular ions through associative ionization. We estimate the rate of molecule formation in excited-state collisions, and directly measure the role of both flux enhancement and excited state survival in the collisional enhancement process. Conceptually simple theoretical models are used to predict the dynamics of the collisional shielding.